Electro-optical Assembly Fabrication

ABSTRACT

A flip-chip bonder fabricates an optical assembly by horizontally positioning a flexible portion of a substrate including a waveguide with the waveguide exposed at one end edge of the substrate; bending a portion of the flexible substrate to place the waveguide exposed end in approximately a vertical position; vertically positioning a bond head containing an optical component upon the waveguide exposed substrate edge to optically mate the optical component with the exposed waveguide; and fixably mounting the optical component to the substrate edge.

RELATED APPLICATION

This patent claims the benefit of the priority date of a prior foreignapplication filed under 35 U.S.C. §119, EPO application numberEPO9178913.1 filed on Dec. 11, 2009 and entitled “Method of Fabricationof an Optical Assembly and Hardware Adapted therefore” which is hereinincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to the manufacturing of opticalsubassemblies and modules.

2. Description of the Related Art

For the manufacturing of optical subassemblies and modules, whichcomprise standard VCSELs (vertical cavity surface emitting laser) andPhotodiodes, one of the main challenges is the very precise alignment ofthese devices with respect to the light carrying medium (i.e. fibres orwaveguides). For optical multi-mode applications, that is. wheremultiple optical modes propagate through the fibres/waveguides,potentially at different speeds, leading to pulse-distortion at higherdata-rates, mechanical alignment accuracies in the order of 5 μm(micrometers) are required.

Many concepts have been proposed in the past, e.g. using passivealignment with different types of packages or optical subassemblies.Very few of them ever made it into a product, mostly because of largescale manufacturing problems and high cost. Independent of the conceptused is the fact that no matter what, at one moment in time theelectro-optical components must be aligned with the required accuracywith respect to either a package, board or a subassembly.

With the constant increase of data-rates and “bandwidth”, newgenerations of systems are carefully considering the need to migrate tooptical transmission to meet product performance targets. So far thelimiting factor has been the cost of producing affordable opticaltransceiver assemblies which convert electrical signals into opticalpulses and on the other end of the signal path to reconvert opticalinputs back into electrical signals. Integration of rigid structures oreven the uses of fibre bundles are complex and cumbersome to the overallsystem architecture.

U.S. Pat. No. 7,336,864 describes an opto-electronic board including aprinted wiring board with an optical waveguide, a metallic area, and ahole, wherein an abutting face of the optical waveguide and an abuttingface of the metallic area form a part of the side face of the hole. Theopto-electronic board further comprises an opto-electronic circuit witha bonding pad, wherein the opto-electronic circuit is arranged in thehole and soldered with its bonding pad to the abutting face of themetallic area.

SUMMARY

In accordance with the present invention, a method is provided tofabricate an optical assembly by horizontally positioning a flexibleportion of a substrate including a waveguide, the waveguide exposed atone end edge of the substrate, bending the flexible portion of thesubstrate to place the waveguide exposed end in approximately a verticalposition, vertically positioning a flip-chip bonder bond head containingan optical component upon the waveguide exposed substrate edge tooptically mate the optical component with the exposed waveguide; andfixably mounting the optical component to the substrate edge.

In a preferred embodiment of the present invention, a method is providedfor fabricating an optical assembly by placing a flexible portion of asubstrate including a waveguide upon a horizontally movable stage of aflip-chip bonder, the waveguide exposed at one end edge of the substratewherein the stage includes an opening positioned underneath thesubstrate exposed end edge, vertically upwardly moving a clamp throughthe stage opening to bend the flexible portion of the substrate to placethe waveguide exposed end in approximately a vertical position,vertically downwardly moving a bond head containing an optical componentupon the waveguide exposed substrate edge to position the opticalcomponent with the exposed waveguide, fixably mounting the opticalcomponent to the substrate edge, and releasing the optical componentfrom the bond head while moving the clamp vertically downward throughthe stage opening to unbend the flexible portion of the substrate withthe optical component mounted.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample with reference to the accompanying drawings in which likereferences denote similar elements, and in which:

FIG. 1 shows a typical flip-chip bonder installation not belonging tothe present invention;

FIGS. 2 a, 2 b, 2 c, 2 d, 2 e and 2 f show an optical assembly andflip-chip bonder in different configurations in accordance with a firstembodiment;

FIG. 3 is a flowchart of the steps of the process described with respectto FIG. 2;

FIGS. 4 a, 4 b and 4 c show a first coupling technique;

FIGS. 5 a, 5 b, and 5 c show a second coupling technique;

FIG. 6 shows parts of a flip-chip bonder adapted for carrying the stepsof the method of FIG. 3;

FIG. 7 shows a substrate comprising multiple optical assemblies; and

FIG. 8 shows a flip-chip bonder adapted for continuous processing.

DETAILED DESCRIPTION

As described above, the precise placement of electro-optical componentsis a critical issue.

Organic optical waveguides on electrical flexible substrates withelectrical fine-pitch conductor technologies can be used as analternative to build the interface between electrical circuits andoptical data-transport-media (e.g. fibres or other waveguides).

With the specific aim of create a path of easy integration of opticsinto IT Systems the use of cheap processes to build electro-optical“flexible” modules is a very powerful tool.

Typically, components are assembled to electrical flex-circuits whilethey're still flat. Only after assembly, the flex circuits are deformedto meet very special spatial requirements (e.g. to “re-orient” opticalcomponents, pressure sensors, microphones, or just to tightly packcomponents into 3-D like assemblies).

FIG. 1 shows a typical flip-chip bonder installation for flat mountingand not belonging to the present invention. As shown, there is provideda substrate 130 upon which a flip-chip component 120 is to be installed.The flip-chip bonder itself comprises bond head 110 and X-Y stage 140.The substrate 130 is mounted on the X-Y stage 140, which is adapted tocoarsely position the substrate in the x-y plane. The flip-chipcomponent 120 meanwhile is held by bond head 110. The bond head 110 ismounted for precise movement in the z-axes. As shown, the bond head isprovided with airtight channels 111 which in use contain a partialvacuum, thereby retaining the flip-chip component in position on the diehead. The bond head 110 and X-Y stage 140 are moved so as to preciselyalign the substrate 130 and flip-chip component 120 in the desiredrelationship, and then the bond-head is moved in the z axis so as tobring the flip-chip component into contact with the substrate 130 suchthat optical apertures on the flip-chip component 130 are exactlyaligned with corresponding apertures of the waveguides. The flip-chipcomponent 120 is then bonded to the substrate 130 by any one of a numberof standard techniques such as use of thermal curing glue, use of UVcuring glue, use of rapidly curing glue etc. The bond head 110 thenpressurises the channels 111 so as to release the flip-chip componentand withdraws.

A standard flip-chip bonder of the kind described above has the requiredprecision to position optical components, and present the furtheradvantage of being readily available and relatively inexpensive. Thevery high placement accuracy, inherent to flip-chip bonders is used todirectly attach optical devices to the optical facet, or terminal of awaveguide or waveguide array and to use the flexible nature offlex-prints to orient the latter in a suitable way to be processed withstandard equipment, that is connected to an electro-optical chip die(e.g. a VCSEL or a photodiode) by means of a standard flip-chip bonder.The optical wave-guides are manufactured on either side of the substrateor fully embedded. The expression “optical device” electro-opticalcomponent such as for example a Photodiode or VCSEL, or a passivecomponent such as a lens or mirror.

Unfortunately many optical components are intended for mounting in thez-y plane, i.e. at right angles to the plane of the substrate, so as toreceive or transmit an optical signal arriving through a waveguideoriented in the plane of the substrate.

Embodiments described herein seek to exploit the intrinsic flexibilityof flex-circuits, even before certain components have yet beenassembled, i.e. to use the flexibility of the substrate to enable asimpler and higher throughput assembly operation.

FIGS. 2 a, 2 b, 2 c, 2 d, 2 e and 2 f show an optical assembly andflip-chip bonder in different configurations in accordance with a firstembodiment of this invention.

As shown in FIG. 2 a there is provided a rectangular, planar, flexiblesubstrate 230, comprising one or more waveguides 235. The flexiblesubstrate is provided with a reinforcing layer 231. As shown, a U shapedsection is cut out from the substrate 230 to leave a tongue 234 fixed tothe substrate at one edge. To guarantee the terminal remain properlyaligned (i.e. no warping) and increase the surface available forbonding, a further reinforcing section in the form of a piece of rigidPCB material 232 is added/left underneath the tongue portion 234, butthere is provided an un-reinforced, flexible portion 233 extendingacross the width of the tongue 234.

As a preliminary step, the x-y stage (not shown) positions the planarsubstrate 230 on the panel underneath the bond-head 260, which as shownincludes the optical component 250.

As shown, there is further provided a clamp element 240, situated belowthe bond head 260, which once the planar substrate 230 is correctlypositioned with respect to the x-y plane starts to rise upwards towardsthe planar substrate 230 and bond head 260 in the z axis.

As shown in FIG. 2 b, the clamp element 240, has risen upwards to thebond head 260 in the z axis so as to engage the planar substrate 230 andby the pressure exerted thereon has deformed at least a part of theflexible portion, so that the terminal 235 of the waveguide comprisedtherein is oriented away from the substrate 230 so as to expose theterminal 235. In particular as shown the terminal 235 is positioned in abonding plane 237 substantially parallel to the plane of the substrate230, and elevated above it.

The x-y stage (not shown) is formed to permit the passage of the clamp,for example by the provision of an aperture of suitable dimensions.

As shown, the clamp element 240 is shaped so to as to exactly conform tothe outer contour of the flexible portion of the planar substrate in itsdeformed configuration, so as to ensure that the terminal 235 isprecisely and securely positioned with respect to the x-y stage, andthereby the bond head 260.

To further avoid undesired deformations of the substrate, the x-y stageand/or the clamping element may be provided with gripping means such asan adhesive or high friction coating, suction cups or vacuum channels,similar to those provided in the bond head.

According to an optional variation of the embodiment of FIG. 2, theremay be provided a second clamp element. This second clamp element ispreferably shaped so as to exactly conform to the inner contour of theflexible portion of the planar substrate in its deformed configuration,that is, on the opposite side of the substrate to the first clampelement. By this means, any residual freedom for the terminal to strayfrom the required position is removed, so as to ensure that the terminal235 (not shown) is precisely and securely positioned with respect to thex-y stage, and thereby the bond head 260. Where such a second clampelement is provided, it may advantageously be brought into contact withthe substrate by sliding in sideways parallel the substrate, or morepreferably by arriving obliquely from above so as to clear anycomponents on the substrate surface.

In certain embodiments, the x-y stage and/or the bond-head may also beable to correct angular errors with respect to the orientation of theplanar substrate (i.e. tilt and rotation).

As shown in FIG. 2 c, once the terminal 235 (not shown) is correctlypositioned with regard to x- and y and θ, t, and where appropriate tiltand rotation, the bond head positions the optical component in the zaxis so as to placing the electro-optical component on the waveguidecomponent by means of a flip-chip bonder so as to abut the terminal, asshown in FIG. 2 d. The bond head is provided with airtight channels 261which in use provide a partial vacuum, thereby retaining the flip-chipcomponent in position on the die head as discussed above with respect toFIG. 1.

It is at this stage that the electro-optical component is coupled to theterminal, as described in more detail hereafter.

As shown in FIG. 2 e, the bond head 260 then pressurises the channels261 so as to release the optical component 250 and withdraws. Meanwhile,the clamp element 240 is also withdrawn, so that the flexible portion soas to resume its position aligned with the plane of the substrate, asshown in FIG. 2 f. This deformation preferably occurs due to theelasticity of the flexible substrate.

FIG. 2 f thus shows the optical assembly in its final form, with theoptical component 250 positioned so as to receive an optical signal froma waveguide oriented in the plane of the substrate, and to transmit asignal away from that plane, for example at right angles thereto.

It will be appreciated that the configuration of the substrate may besubject to many variations. For example, the reinforcing layer may beomitted altogether, or may take a different form to that describedabove. The reinforcing layer may include only the main section 231, orthe part reinforcing the tip of the tongue 232. The reinforcing layermay be disposed on either or both sides of the flexible substrate.Rather than comprising a cutout defining a tongue 234 as describedabove, the flexible portion may be a protuberance extending from theedge of the substrate, or indeed the whole width of the flexiblesubstrate may constitute the flexible portion, in which case thedeformation step would involve the bending of the whole substrate acrossits width.

FIG. 3 is a flowchart of the steps of the process described with respectto FIGS. 2 a-2 f. There is accordingly defined a method for fabricatingan optical assembly comprising an optical component. As shown in FIG. 3,the method starts at step 300, at which a planar substrate 230comprising a waveguide portion 234 through which a waveguide extends isprovided. The waveguide portion comprises a flexible portion 233 suchthat by deformation of at least a part of the flexible portion 233, thesubstrate 230 may be arranged in an operational configuration with aterminal 235 of the waveguide positioned within the plane so as tointerface an installed optical component in operation, and aninstallation configuration with the terminal of the waveguide orientedaway from the substrate so as to expose the terminal 235 forinstallation of the optical component 250. The method then proceeds tostep 305, at which the flexible portion 233 is deformed so as to adoptthe installation configuration. The method then proceeds to step 310 atwhich the electro-optical component is placed on the waveguide portion234 by means of a flip-chip bonder 260 so as to abut the terminal 235.The method then proceeds to step 315 at which the electro-opticalcomponent is coupled to the terminal, before finally proceeding to step320 of deforming the flexible portion so as to adopt the operationalconfiguration.

As described with reference to FIGS. 2 a-2 f, the waveguide portionpreferably comprises a tongue fixed to the substrate at one edge, andwherein the flexible portion 233 extends across the width of the tongue.

As described with reference to FIG. 2 b, the installation configurationof the terminal 235 is preferably positioned in a plane substantiallyparallel to the plane of the substrate.

As described with reference to FIG. 2 f, in the operationalconfiguration the terminal is preferably positioned in a planesubstantially orthogonal to the plane of the substrate.

As described with reference to FIGS. 2 e and 2 f, the step of deformingthe flexible portion so as to adopt the operational configurationpreferably comprises allowing the flexible portion to elastically resumeits original configuration.

Coupling

The step of coupling as described above with regard to FIG. 2 d may beimplemented using a variety of techniques. The term coupling includesthe establishment of different types of relationship between the opticalcomponent 250 and the terminal and the waveguide portion 234. Theserelationships may include the mechanical bonding of the opticalcomponent 250 to the terminal and/or the waveguide portion 234, theoptical coupling of the optical component 250 to the terminal orterminals, and/or the electrical connection of electrical contacts ofthe optical component 250 to electrical contacts of the waveguideportion 234. Electrical connections need only be formed where theoptical component incorporates electrical circuitry. Different couplingtechniques may be envisaged in which two or more of the above kinds ofcoupling are achieved by the same process. A number of exemplarycoupling strategies are described in more detail hereafter; however theskilled person will appreciate that other approaches or differentcombinations of the described techniques may also be effective.

FIGS. 4 a, 4 b, and 4 c show a first coupling technique.

FIGS. 4 a, 4 b and 4 c show an expanded view of the elements of theoptical assembly at the interface between the optical component 250 andthe substrate 230. In particular, the free end of the flexible portion234 is shown in the installation configuration, together with thereinforcing part 232. FIG. 4 a further shows the waveguide 400, and theterminal 235.

In FIG. 4 a, the optical component 250 has not yet been brought intocontact with the terminal 235. The optical device and the bond-surfaceare prepared. The lower surface of the optical component 250 has beenprovided with a plurality of stand-off bumps 410, which may compriseelectrical contacts e.g. Gold-stud-bumps and/or mechanical stand-offs.

On the flexible substrate a fast curing glue (e.g. photosensitive glue)for the mechanical fixation is deposited. To reduce the impact ofpotential spill-over of this mechanical glue over the optical interface,an optically transparent glue is preferable. The contact material forthe electrical contacts (e.g. conductive epoxy) is deposited by e.g.stencil printing. As shown, an electrically conductive glue 420 has beenapplied to the substrate 230, in electrical contact with conductivetracks embedded in said substrate or disposed on the surface thereof.Still further, an optically curable glue 430 has been applied to thesubstrate 230 and/or preferably to the reinforcing layer 232.

In FIG. 4 b, the optical component 250 has been brought into contactwith the substrate, or more precisely certain stand-off bumps 410mounted on the optical component 250 have been brought into contact withthe substrate, thereby spacing the optical component itself at aprecisely controlled distance from the terminal 235. Certain stand-offbumps 410 are in contact with the optically curable glue 430, and othersare in contact with the electrically conductive glue 420, so thatcertain stand-off bumps also form part of the electrical contact betweenthe optical component 250 and the substrate 230. At this stage the gluesare cured. By exposure to suitable radiation such as ultra-violet lightin the case of optically curable glues, or by exposure to heat in thecase of thermally cured glues, or otherwise as appropriate. The opticalcomponent is now physically secured to the substrate, and the bond head260 may be withdrawn as described above.

In FIG. 4 c, an optical underfill 440 is injected between theelectro-optical component 250 and the terminal 235, in the cavitycreated by the stand-off bumps 410. The optical underfill 440 is thencured. Once cured, the optical underfill optically couples the opticalcomponent and the terminal 235, and is thus preferably selected to havesuitable transparency and refractive properties to ensure propertransmission of optical signals once cured.

Thus with respect to mechanical coupling, there are accordingly providedsteps of applying a glue to the flexible portion in the vicinity of theterminal, wherein the step of placing the electro-optical componentcomprises bringing the electro-optical component into contact with theglue, and wherein in the step of coupling the electro-optical componentto the terminal comprises the further step of physically securing theelectro-optical component to the terminal by curing the glue. The glueis preferably substantially transparent, so that in the event of a spillof glue into the vicinity of the terminal, the glue will present aminimal interference to correct signal transmission. The glue ispreferably optically curable, since this permits excellent control ofthe timing of the curing process, without exposing the assembly toundesirable thermal or chemical environments.

Thus with respect to electrical coupling, there are accordingly providedsteps of providing an interface surface of the electro-optical componentwith a plurality of stand-off bumps, and of applying an electricallyconductive glue to the flexible portion in electrical connection withthe terminal, wherein the step of placing the electro-optical componentcomprises bringing at least one of the stand-off bumps into contact withthe electrically conductive glue, and wherein in the step of couplingthe electro-optical component to the terminal comprises the further stepof electrically connecting the electro-optical component to the terminalby curing the glue. The glue may be a solder, in which case a reflow orother processing method may be appropriate. This step need not beperformed on the flip-chip bonder because mechanically the device mayalready be secured mechanically by the mechanical glue.

Thus with respect to optical coupling, there are accordingly providedsteps of injecting and subsequent curing an optical underfill betweenthe electro-optical component and the terminal.

Another approach to establishing electrical coupling may comprises thefurther steps of bringing at least one of the contacts in closeproximity to a corresponding electrical contact on the terminal anddepositing an electrically conductive material such as a conductive ink.The deposition of electrically conductive ink may advantageously beachieved by inkjet-printing.

There may optionally be provided cleaning steps. These steps mayadvantageously be implemented after the mechanical securing of theoptical component 250 to the substrate 230, and before the opticalinterface is sealed by applying an optically transparent underfillmaterial, which also further improves the mechanicalattachment/stability.

FIG. 5 shows a second coupling technique.

FIG. 5 shows an expanded view of the elements of the optical assembly atthe interface between the optical component 250 and the substrate 230.In particular, the free end of the flexible portion 234 is shown in theinstallation configuration, together with the reinforcing part 232. FIG.5 further shows the waveguide 400, and the terminal 235.

In FIG. 5 a, the optical component 250 has not yet been brought intocontact with the terminal 235. The optical device and the bond-surfaceare prepared. The lower surface of the optical component 250 has beenprovided with electrical conductor contacts 540. The contact materialfor the electrical contacts (e.g. conductive epoxy) is deposited by e.g.stencil printing.

The upper surface of the flexible substrate 230 has similarly beenprovided with electrical conductor contacts 520. The contact materialfor the electrical contacts (e.g. conductive epoxy) are again depositedby e.g. stencils printing. On the flexible substrate a fast curing glue530 (e.g. photosensitive glue) for the mechanical fixation is deposited.Since this glue also fulfils the role of optical coupling agent, thismaterial must also have suitable optical properties once cured. The fastcuring glue may equally be provided either on the optical device or onthe substrate or on both.

In FIG. 5 b, the optical component 250 has been brought to a preciselycontrolled distance from the terminal 235, with the glue 530 sandwichedbetween the substrate and the optical component so as to substantiallyfill all of the space between the two elements. In fact it is onlynecessary that contact is made, and that a maximum distance, for examplesmaller than ˜50 microns), is preferably not exceeded. The electricalcontacts 540 and 520 are in close proximity, but may be separated by abead of glue 530 squeezed from between the substrate and the opticalcomponent. At this stage the glues are cured, by exposure to suitableradiation such as ultra-violet light in the case of optically curableglues, or by exposure to heat in the case of thermally cured glues, orotherwise as appropriate. The optical component is now physicallysecured to the substrate, and the bond head 260 may be withdrawn asdescribed above. The bead of glue 530 squeezed from between thesubstrate and the optical component may be excised by means of a laseror otherwise, so as to leave the electrical contacts 540 and 520separated by a mere film of glue.

In FIG. 5 c, a connecting film of conductive ink or other electricallyconductive material 550 is printed for example by means of an inkjetprinter so as to bridge the gap between electrical contacts 540 and 520.

FIG. 6 shows parts of a flip-chip bonder adapted for carrying the stepsof the method of FIG. 3. As shown, the flip-chip bonder comprises a bondhead 260 comprising channels 261 as described above, and a lower clampelement 240. The flip-chip bonder further comprises an x-y stage 610,and an upper clamping element 620. The x-y stage is moveable such that aplanar substrate mounted thereon can be positioned in the x-y plane withrespect to the other components, and is provide with an aperture for thepassage of a lower clamp element 240. An optional upper clamp element isarticulated so as to move inward the other components being articulatedso as to engage the surface of a substrate mounted on the x-y stage,such that by trapping the substrate between the upper and lower clampelements at least a part of a flexible portion deformation of thesubstrate may be arranged in an installation configuration with theterminal of the waveguide oriented away from the substrate so as toexpose the terminal for installation of the optical component, whereuponthe bond head 260 is adapted to descend in the z axis to bring anoptical component into contact with the substrate.

By withdrawing the bond head and upper and lower clamp elements, theflexible portion is allowed to resume its original configuration.

The flip-chip bonder may additionally be provided with means for theinjection or placement of glues or solders for coupling of the opticalcomponent to the substrate.

The flip-chip bonder may additionally be provided with means for thecuring of glues used in the coupling of the optical component to thesubstrate, such as ultra-violet lamps or heaters.

As described above, a single optical assembly is formed from a givensubstrate, by coupling a single optical component thereto. It will beappreciated that a given assembly comprise a plurality of opticalcomponents, in which case a corresponding plurality of bond heads, or aspecially adapted composite bond head, or a single bond head controlledso as to sequentially place each of the plurality of optical componentswill be required. It will furthermore be appreciated that a plurality ofassemblies may be formed on the same substrate, for later separation,thereby making better use of the relatively large range of travel of thex-y stage.

FIG. 7 shows a substrate comprising multiple optical assemblies.

As shown in FIG. 7 there is provided a substrate 730 bearing eightcut-out tongue portions 731 to 738, ready for installation of opticalcomponents as described above. The eight cut-out tongue portions 731 to738 are arranged in a 2×4 matrix. The x-y stage of the flip-chip bonderwould preferably be adapted to mirror this configuration, in particularby being sufficiently large to support the entire substrate, andproviding an aperture corresponding to each assembly for the passage ofthe lower clamp element 240 as described above. Such a “panel levelassembly” promises to be more efficient and allows for a higher assemblythroughput.

Still further, the substrate of FIG. 7 may constitute a continuous web.By further adaptations to the flip-chip bonder it is then possible toproduce optical assemblies in a continuous process, rather than thebatch process described heretofore.

FIG. 8 shows a flip-chip bonder adapted for continuous processing.

The flexible waveguide is processed in sequence in different processstations. A continuous reel of flexible substrate 861 is provided. Inthe place of the x-y stage there is provided a conveyor belt 869, whichis provided with regularly spaced aperture for the passage of the lowerclamp element 240. Material is drawn from this reel 861 through thevarious stages of the adapted flip-chip-bonder to produce complete acontinuous stream of complete optical assemblies at the output. Onleaving the reel, a particular section of substrate material firstpasses dispensing steps 863 and 862 which in accordance with theforegoing embodiments dispense optical glue for mechanical attachmentand optical coupling and electrically conductive glue such as epoxy,respectively.

The substrate material next arrives between the bond head 260 and thelower clamp 240, whereupon the optical component is positioned andcoupled as described above. A flash curing station 865 radiates theassembly with a suitable (ultra-violet) radiation to cure opticallycurable glues etc. as appropriate. The assembly is moved on to a furtheroptical sealing polymer dispenser 866 which dispenses opticalunderfilling on the case of mechanical stand-offs in accordance withforegoing embodiments, and then cut from the continuous substrate web toform an individual assembly by cutter unit 867. The assembly then passesthrough an oven 868 for thermal curing of thermally activated glues asappropriate, in particular for the applied optical polymer dispensed bydispenser 866 as well as any other curable glues, e.g. UV curable glues,to which no UV could be applied because they were masked by thecomponents themselves at the earlier step.

This approach makes it possible to manufacture flexible cables of anygiven length bearing optical and Opto/Electrical conversions at eitherends of the cable. Optical Waveguide can be produced of pre-configuredcustomised lengths onto a flexible tape or reel

This approach can be highly efficient, since the rough-alignmentrequirements (i.e. through the part-feeder) is not very high and thefine-adjustments is done by the Flip-chip bonder, which have usuallyusable path lengths in the order of 25 mm.

By using butt-coupling as described above with regard to the secondembodiment, directly to the waveguides with minimum distance between theoptical components and the waveguides, it is very likely that thealignment accuracy can be relaxed from ˜5 μm to somewhere between 10 to20 μm.

According to further embodiments, a flip-chip bonder is used to mountoptical components including electro-optical components on a flexiblesubstrate bearing waveguides by bending a part of the substrate out ofits plane so as to expose the waveguide terminals, positioning theoptical component on the exposed terminal, bonding it in place and thenallowing the substrate to return to its plane. To facilitate thisapproach the flip-chip bonder may be adapted to incorporate one or moreclamp elements to deform the substrate in the appropriate manner tocorrectly expose and position the terminal. The bonder x-y stage may beprovided with an aperture to allow the passage of such clamp elements. Acontinuous reel process is also provided, capable of producingsubstrates or cables of any arbitrary length with optical componentsmounted at either end.

The invention can take the form of an entirely hardware embodiment, asembodied in the flip-chip bonder, an entirely software embodiment asembodied for example in software controlling the flip-chip bonder, or anembodiment containing both hardware and software elements. In apreferred embodiment, the invention is implemented in software, whichincludes but is not limited to firmware, resident software, microcode,etc.

Furthermore, the invention can take the form of a computer programproduct accessible from a computer-usable or computer-readable mediumproviding program code for use by or in connection with a computer orany instruction execution system. For the purposes of this description,a computer-usable or computer readable medium can be any apparatus thatcan contain, store, communicate, propagate, or transport the program foruse by or in connection with the instruction execution system,apparatus, or device.

The medium can be an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system (or apparatus or device) or apropagation medium. Examples of a computer-readable medium include asemiconductor or solid state memory, magnetic tape, a removable computerdiskette, a random access memory (RAM), a read-only memory (ROM), arigid magnetic disk and an optical disk. Current examples of opticaldisks include compact disk-read only memory (CD-ROM), compactdisk-read/write (CD-R/W) and DVD.

Accordingly there is provided a computer program comprising instructionsfor controlling a flip-chip bonder so as to install an optical componentin an optical assembly, said assembly comprising:

a planar substrate comprising a waveguide portion through which awaveguide extends, said waveguide portion comprising a flexible portionsuch that by deformation of at least a part of the flexible portion, thesubstrate may be arranged in an operational configuration with aterminal of the waveguide oriented within the plane so as to interfacean installed optical component in operation, and an installationconfiguration with the terminal of the waveguide oriented away from thesubstrate so as to expose the terminal for installation of the opticalcomponent,

said computer program causing said flip-chip bonder suitably coupled toa computer executing said program to implement the steps of:

deforming the flexible portion so as to adopt the installationconfiguration;

placing the electro-optical component on the waveguide component bymeans of a flip-chip bonder so as to abut the terminal;

coupling the electro-optical component to the terminal; and

deforming the flexible portion so as to adopt the operationalconfiguration.

The computer may of course be embedded in the flip-chip bonder, or be astand alone computer coupled to the flip-chip bonder by any appropriatemeans, for example via an Ethernet or wireless network connection, USB,Bluetooth etc as appropriate.

A data processing system suitable for storing and/or executing programcode will include at least one processor coupled directly or indirectlyto memory elements through a system bus. The memory elements can includelocal memory employed during actual execution of the program code, bulkstorage, and cache memories which provide temporary storage of at leastsome program code in order to reduce the number of times code must beretrieved from bulk storage during execution.

Input/output or I/O devices (including but not limited to keyboards,displays, pointing devices, etc.) can be coupled to the system eitherdirectly or through intervening I/O controllers.

Network adapters may also be coupled to the system to enable the dataprocessing system to become coupled to other data processing systems orremote printers or storage devices through intervening private or publicnetworks. Modems, cable modem and Ethernet cards are just a few of thecurrently available types of network adapters.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the Figures. For example, twoblocks shown in succession may, in fact, be implemented substantiallyconcurrently, or the blocks may sometimes be implemented in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art that basedupon the teachings herein, that changes and modifications may be madewithout departing from this invention and its broader aspects.Therefore, the appended claims are to encompass within their scope allsuch changes and modifications as are within the true spirit and scopeof this invention. Furthermore, it is to be understood that theinvention is solely defined by the appended claims. It will beunderstood by those with skill in the art that if a specific number ofan introduced claim element is intended, such intent will be explicitlyrecited in the claim, and in the absence of such recitation no suchlimitation is present. For non-limiting example, as an aid tounderstanding, the following appended claims contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimelements. However, the use of such phrases should not be construed toimply that the introduction of a claim element by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim element to inventions containing only one such element,even when the same claim includes the introductory phrases “one or more”or “at least one” and indefinite articles such as “a” or “an”; the sameholds true for the use in the claims of definite articles.

1. A method for fabricating an optical assembly comprising: horizontallypositioning a flexible portion of a substrate including a waveguide, thewaveguide exposed at one end edge of the substrate; bending the flexibleportion of the substrate to place the waveguide exposed end inapproximately a vertical position; vertically positioning a flip-chipbonder bond head containing an optical component upon the waveguideexposed substrate edge to optically mate the optical component with theexposed waveguide; and fixably mounting the optical component to thesubstrate edge.
 2. A method according to claim 1 further including astep of unbending the portion of the flexible substrate with the mountedoptical component thereon.
 3. A method for fabricating an opticalassembly comprising: placing a flexible portion of a substrate includinga waveguide upon a horizontally movable stage of a flip-chip bonder, thewaveguide exposed at one end edge of the substrate wherein the stageincludes an opening positioned underneath the substrate exposed endedge; vertically upwardly moving a clamp through the stage opening tobend the flexible portion of the substrate to place the waveguideexposed end in approximately a vertical position; vertically downwardlymoving a bond head containing an optical component upon the waveguideexposed substrate edge to position the optical component with theexposed waveguide; fixably mounting the optical component to thesubstrate edge; and releasing the optical component from the bond headwhile moving the clamp vertically downward through the stage openingthereby unbending the flexible portion of the substrate with the opticalcomponent mounted thereon.
 4. The method according to claim 3 whereinthe clamp grips the portion of the flexible portion of the substrateduring the upwardly moving step to bend the substrate.
 5. The methodaccording to claim 4 wherein the clamp includes a high friction surfaceto grip the substrate portion.
 6. The method of claim 3 furtherincluding the step of placing a first reinforcement layer upon thesubstrate end portion.
 7. The method of claim 6 wherein the clampengages the first reinforcement layer.
 8. The method of claim 3 whereinthe bond head includes at least one vacuum channel to contain theoptical component.
 9. The method of claim 3 wherein the step of fixablymounting the optical component to the substrate edge includes the stepsof providing mechanical stand-offs upon a mating surface of the opticalcomponent, providing glue between the exposed waveguide substrate edgeand the optical component mating surface, and positioning the opticalcomponent upon the exposed waveguide substrate edge to distribute theglue.
 10. The method of claim 3 wherein the step of fixably mounting theoptical component to the substrate edge includes the steps of providingat least one electrical contact upon a mating surface of the opticalcomponent, providing an electrical contact upon a surface of thesubstrate, placing glue between the optical component mating surface andthe exposed waveguide substrate edge, and positioning the opticalcomponent upon the exposed waveguide substrate edge to distribute theglue.
 11. A system for fabricating an optical assembly comprising: ahorizontally movable stage of a flip-chip bonder including having anopening; a substrate including at least one flexible portion and furtherincluding a waveguide, the waveguide exposed at one end edge of thesubstrate positioned upon the stage with the end edge over the opening;a vertically upwardly movable clamp sized to penetrate the stage openingand positioned underneath the stage; a vertically downwardly movablebond head above the stage opening; an optical component positioned inthe bond head; a glue dispenser positioned to provide a glue to either amating surface of the substrate exposed end edge or a mating surface ofthe optical component; and a controller connected to the stage, theclamp, the bond head and the glue dispenser including a control circuitfor positioning the substrate waveguide exposed end edge underneath theoptical component while dispensing glue for fixably bonding the matingsurfaces of the optical component and the substrate exposed end edge.12. A system according to claim 11 wherein the clamp includes a curvedsurface to engage the substrate.
 13. A system according to claim 11wherein the substrate includes a reinforcing strip located beneath asubstrate portion adjacent to the substrate exposed end edge.
 14. Asystem according to claim 13 wherein the clamp includes a curved surfaceto engage the substrate and further includes a formation sized to engagethe reinforcing strip.
 15. A computer program product for fabricating anoptical assembly, the computer program product comprising: a computerreadable storage medium having computer readable program code embodiedtherewith, the computer readable program code comprising; first computerreadable program code configured to horizontally position a flexibleportion of a substrate including a waveguide, the waveguide exposed atone end edge of the substrate; second computer readable program codeconfigured to bend the flexible portion of the substrate to place thewaveguide exposed end in approximately a vertical position; thirdcomputer readable program code configured to vertically position aflip-chip bonder bond head containing an optical component upon thewaveguide exposed substrate edge to optically mate the optical componentwith the exposed waveguide; and fourth computer readable program codeconfigured to fixably mount the optical component to the substrate edge.16. A computer program according to claim 15 further including a fifthcomputer readable program code configured to unbend the flexible portionof the substrate with the mounted optical component thereon.
 17. Acomputer program product for fabricating an optical assembly, thecomputer program product comprising: a computer readable storage mediumhaving computer readable program code embodied therewith, the computerreadable program code comprising; first computer readable program codeconfigured to place a flexible portion of a substrate including awaveguide, the waveguide exposed at one end edge of the substrate upon ahorizontally movable stage of a flip-chip bonder wherein the stageincludes an opening positioned underneath the substrate exposed endedge; second computer readable program code configured to verticallyupwardly move a clamp through the stage opening to bend the flexibleportion of the substrate to place the waveguide exposed end inapproximately a vertical position; third computer readable program codeconfigured to vertically downwardly move a bond head containing anoptical component upon the waveguide exposed substrate edge to positionthe optical component with the exposed waveguide; fourth computerreadable program code configured to fixably mount the optical componentto the substrate edge; and fifth computer readable program codeconfigured to release the optical component from the bond head whilemoving the clamp vertically downward through the stage opening therebyunbending the flexible portion of the substrate with the opticalcomponent mounted thereon.
 18. The computer program product according toclaim 17 wherein the second computer readable program code furtherincludes program code to grip the flexible portion of the substrate bythe clamp during the upwardly moving step to bend the substrate.
 19. Thecomputer program product according to claim 17 wherein the firstcomputer readable program code further includes program code to place afirst reinforcement layer upon a substrate end portion.
 20. The computerprogram product according to claim 17 wherein the fourth computerreadable program code further includes program code to provide at leastone electrical contact upon a mating surface of the optical component,provide an electrical contact upon a surface of the substrate, placeglue between the optical component mating surface and the exposedwaveguide substrate edge, and position the optical component upon theexposed waveguide substrate edge to distribute the glue.